1,139 research outputs found
Imprint of the stochastic nature of photon emission by electrons on the proton energy spectra in the laser-plasma interaction
The impact of stochasticity effects (SEs) in photon emissions on the proton
energy spectra during laser-plasma interaction is theoretically investigated in
the quantum radiation-dominated regime, which may facilitate SEs experimental
observation. We calculate the photon emissions quantum mechanically and the
plasma dynamics semiclassically via two-dimensional particle-in-cell
simulations. An ultrarelativistic plasma generated and driven by an
ultraintense laser pulse head-on collides with another strong laser pulse,
which decelerates the electrons due to radiation-reaction effect and results in
a significant compression of the proton energy spectra because of the charge
separation force. In the considered regime the SEs are demonstrated in the
shift of the mean energy of the protons up to hundreds of MeV. This effect is
robust with respect to the laser and target parameters and measurable in soon
available strong laser facilities
Low temperature x-ray diffraction study on superconductivity
金沢大学理工研究域Using a low temperature x-ray diffractometer, we studied superconductivity materials, optimally doped and underdoped YBCOs and PrOs4Sb 12 between 0.1 K and 300 K. At several temperatures, whole profiles of the x-ray reflection peak were measured and refined by Rietveld analysis. By Rietveld analysis, we found that Pr atoms in PrOs4Sb12 are still oscillating at an amplitude of about 0.1 A at 0.18 K. For some reflection planes, x-ray diffraction measurement with a small step size and a long stepping time was performed to accumulate more counts at certain temperatures. The lattice constant d of optimally doped YBCO (OPT YBCO) shows anomalous behaviours at around the superconductivity transition temperature Tc and around spin gap temperature T*. In OPT YBCO, the intensity of the reflection spectrum shows a clear anomaly at around Tc. © 2009 IOP Publishing Ltd
Determining Heavy Hybrid Masses via QCD Sum Rules
The masses of charmonium and bottomonium hybrids are evaluated in
terms of QCD sum rules. We find that the ground state hybrid in charm sector
lies in GeV, while in bottom sector the hybrid may
situated in GeV. Since the numerical result on
charmonium hybrid mass is not compatible with the charmonium spectra, including
structures newly observed in experiment, we tempt to conclude that such a
hybrid does not purely exist, but rather as an admixture with other states,
like glueball and regular quarkonium, in experimental observation. However, our
result on bottomonium hybrid coincide with the "exotic structure" recently
observed at BELLE.Comment: 15 pages, 5 figures, version to appear in J.Phys.
The effects of degree correlations on network topologies and robustness
Complex networks have been applied to model numerous interactive nonlinear
systems in the real world. Knowledge about network topology is crucial for
understanding the function, performance and evolution of complex systems. In
the last few years, many network metrics and models have been proposed to
illuminate the network topology, dynamics and evolution. Since these network
metrics and models derive from a wide range of studies, a systematic study is
required to investigate the correlations between them. The present paper
explores the effect of degree correlation on the other network metrics through
studying an ensemble of graphs where the degree sequence (set of degrees) is
fixed. We show that to some extent, the characteristic path length, clustering
coefficient, modular extent and robustness of networks are directly influenced
by the degree correlation.Comment: 13 pages, 6 figure
Robust PID based indirect-type iterative learning control for batch processes with time-varying uncertainties
ased on the proportional-integral-derivative (PID) control structure widely used in engineering applications, a robust indirect-type iterative learning control (ILC) method is proposed for industrial batch processes subject to time-varying uncertainties. An important merit is that the proposed ILC design is independent of the PID tuning that aims primarily to hold robust stability of the closed-loop system, owing to the fact that the ILC updating law is implemented through adjusting the setpoint of the closed-loop PID control structure plus a feedforward control to the plant input from batch to batch. According to the robust H infinity control objective, a robust discrete-time PID tuning algorithm is given in terms of the plant state-space model description to accommodate for time-varying process uncertainties. For the batchwise direction, a robust ILC updating law is developed based on the two-dimensional (2D) control system theory. Only measured output errors of current and previous cycles are used to implement the proposed ILC scheme for the convenience of practical application. An illustrative example from the literature is adopted to demonstrate the effectiveness and merits of the proposed ILC method
Measurement of the chi_{c2} Polarization in psi(2S) to gamma chi_{c2}
The polarization of the chi_{c2} produced in psi(2S) decays into gamma
chi_{c2} is measured using a sample of 14*10^6 psi(2S) events collected by
BESII at the BEPC. A fit to the chi_{c2} production and decay angular
distributions in psi(2S) to gamma chi_{c2}, chi_{c2} to pi pi and KK yields
values x=A_1/A_0=2.08+/-0.44 and y=A_2/A_0=3.03 +/-0.66, with a correlation
rho=0.92 between them, where A_{0,1,2} are the chi_{c2} helicity amplitudes.
The measurement agrees with a pure E1 transition, and M2 and E3 contributions
do not differ significantly from zero.Comment: 6 pages, 4 figures, 1 tabl
Measurement of the branching fractions of psi(2S) -> 3(pi+pi-) and J/psi -> 2(pi+pi-)
Using data samples collected at sqrt(s) = 3.686GeV and 3.650GeV by the BESII
detector at the BEPC, the branching fraction of psi(2S) -> 3(pi+pi-) is
measured to be [4.83 +- 0.38(stat) +- 0.69(syst)] x 10^-4, and the relative
branching fraction of J/psi -> 2(pi+pi-) to that of J/psi -> mu+mu- is measured
to be [5.86 +- 0.19(stat) +- 0.39(syst)]% via psi(2S) -> (pi+pi-)J/psi, J/psi
-> 2(pi+pi-). The electromagnetic form factor of 3(pi+pi-) is determined to be
0.21 +- 0.02 and 0.20 +- 0.01 at sqrt(s) = 3.686GeV and 3.650GeV, respectively.Comment: 17pages, 7 figures, submitted to Phys. Rev.
Measurements of J/psi decays into phi pi^0, phi eta, and phi eta^prime
Based on 5.8x10^7 J/psi events detected in BESII, the branching fractions of
J/psi--> phi eta and phi eta^prime are measured for different eta and eta^prime
decay modes. The results are significantly higher than previous measurements.
An upper limit on B(J/psi--> phi pi^0) is also obtained.Comment: 9 pages, 10 figure
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